Effects of Elevated Ozone Concentration on Starch and Starch Synthesis Enzymes of Yangmai 16 Under Fully Open-Air Field Conditions

O3 is not only greenhouse gas but also a primary gaseous contaminant in the atmosphere.It has long-lasting effects on crop growth,yield and quality,and brings a series of ecological and environmental problems.A free-air controlled enrichment（FACE） system was applied to study the effect of elevated ozone concentration on activities of key enzymes of starch synthesis of Yangmai 16 in 2009-2010.The main-plot treatment had two levels of O 3 ：ambient level（A-O 3） and 50% higher than ambient level（E-O 3）.The main results were that accumulation rate of amylose,amylopectin and starch were represented in a single peak curve,and their content and accumulation amount rose gradually.The O 3 elevation decreased the accumulation rate of amylose,amylopectin and starch amylase,reduced the accumulation amount of amylopectin and starch,and decreased the content of amylopectin and starch,but increased the content of amylose.With the increase of O 3 concentration,the enzyme activity of grain granule-bound starch synthase（GBSS）,soluble starch synthase（SSS） and starch branching enzyme（SBE） decreased after anthesis.The activities of GBSS and SSS had highly significant correlations with amylose,amylopectin and starch accumulation rate,and the activity of SBE had significant correlations with these items.So the O 3 elevation decreased the activity of key enzymes of starch synthesis,which led to the variation of starch synthesis.

Effects of NaCI and Ca^(2+) on Membrane Potential of Epidermal Cells of Maize Roots

The effects of salt-stress on plants involve not only the water stress caused by low osmotic pressure, but also the toxicity of excess Na^＋. A large amount of Na^＋ entering cells would reduce K^＋ uptake, which leads to an imbalance of K：Na ratio in cells. One of the reasons for the reduced K^＋-uptake is the closure of K^＋-channel which is controlled by membrane potential. Calcium is usually applied to improve the growth of plants on saline soils and shows positive influence in the integrality of cell membrane. This study applied glass microelectrode technique to monitoring the NaCl-induced changes of membrane potential of root epidermal cells of maize （Zea mays L., Denghai 11） seedlings at NaCl concentrations of 0, 8, 20, 50, 100, 200 mmol L^-1, respectively. The effect of Ca^2＋ on the changes of membrane potential caused by NaCl was also studied. The results showed that： NaCl caused cell membrane depolarization. The depolarization became greater and faster with increasing of NaCl concentration. Moreover, the extent of depolarization was positively correlated with NaCl concentration. The addition of calcium postponed the depolarization, and decreased the degree of depolarization caused by NaCl. High NaCl concentration leads to depolarization of maize root cell membrane, which can partly be counteracted by calcium.

Functional analysis of helicase and three tandem HRDC domains of RecQ in Deinococcus radiodurans

RecQ is a highly conserved helicase necessary for maintaining genome stability in all organisms. Genome comparison showed that a homologue of RecQ in Deinococcus radiodurans designated as DR1289 is a member of RecQ family with unusual domain arrangement: a helicase domain, an RecQ C-terminal domain, and surprisingly three HRDC domain repeats, whose func-tion, however, remains obscure currently. Using an insertion deletion, we discovered that the DRRecQ mutation causes an increase in gamma radiation, hydroxyurea and mitomycine C and UV sensitivity. Using the shuttle plasmid pRADK, we complemented various domains of the D. radiodurans RecQ (DRRecQ) to the mutant in vivo. Results suggested that both the helicase and helicase-and-RNase-D-C-terminal (HRDC) domains are essential for complementing several phenotypes. The complementation and biochemical function of DRRecQ variants with different domains truncated in vitro suggested that both the helicase and three HRDC domains are necessary for RecQ functions in D. radiodurans, while three HRDC domains have a synergistic effect on the whole function. Our finding leads to the hypothesis that the RecF recombination pathway is likely a primary path of double strand break repair in this well-known radioresistant organism.

A new statistical method for mapping QTLs underlying endosperm traits

Genetic expression for an endosperm trait in seeds of cereal crops may be controlled simultaneously by the triploid endosperm genotypes and the diploid maternal genotypes. However, current statistical methods for mapping quantitative trait loci (QTLs) underlying endosperm traits have not been effective in dealing with the putative maternal genetic effects. Combining the quantitative genetic model for diploid maternal traits with triploid endosperm traits, here we propose a new statistical method for mapping QTLs con- trolling endosperm traits with maternal genetic effects. This method applies the data set of both DNA molecular marker genotypes of each plant in segregation population and the quantitative observations of single endosperms in each plant to map QTL. The maximum likelihood method implemented via the expectation-maximization algorithm was used to the estimate parameters of a putative QTL. Since this method involves the maternal effect that may contribute to en- dosperm traits, it might be more congruent with the genetics of endosperm traits and more helpful to increasing the preci- sion of QTL mapping. The simulation results show the pro- posed method provides accurate estimates of the QTL effects and locations with high statistical power.

Assessment on alien herbicide-resistant gene flow among crucifers by sexual compatibility

Cross-pollination and high cross-compatibility are frequently found in many cruciferous plants, which im-plies that there might be potential risk of alien gene flow among crucifers. In this work, the alien glyphosate-resistant gene flow between GM (Genetically modified) rapeseed vari-ety Q3 (Brassica napus) and 6 varieties from 5 cruciferous species was assessed by sexual compatibility through aniline blue fluorescence observation, manual cross, mentor pollina-tion with the mixture pollen and DNA identification. The results indicated that the compatibility indices of two B. napus varieties, B. juncea var. multiceps Tsen et Lee and Chinese cabbage (B. chinensis) (as female) with Q3 (as male) were 16.15, 12.77, 2.345 and 0.85, respectively. F1 plants were examined by PCR and all of these samples were confirmed as positive. Crossing between Orychophragmus violaceus, Des-curainia sophia (as female) and Q3 (as male) expressed high cross-incompatibility. Fluorescence microscope observation indicated that growing of pollen tube terminated at the upper 1/3 part of the style of O. violaceus and on the stigma surface of D. sophia. The mentor plants were further analyzed by PCR and all were shown to be negative. Under the neighboring growth and natural pollination conditions, the rates of gene flow to two B. napus varieties were 2.3278% and 2.1487%, respectively, B. juncea var. multiceps Tsen et Lee and Chinese cabbage were 1.0157% and 0.9236%, re-spectively. No gene flow was observed in O. violaceus and D. sophia. Frequency of gene flow was highly correlated with sexual compatibility. Due to possible alien gene flow among crucifers, special consideration and care should be taken to grow GM rapeseed.